1. Technical Field
The present invention relates in general to fabricating disks for disk drives and, in particular, to an improved system, method, and apparatus for characterizing, tracking, and segregating known defective regions in patterned magnetic media disks for hard disk drives.
2. Description of the Related Art
Patterned media, discrete track media, or disks with magnetic formatting information created by magnetic lithography or printing processes have inherent, repeatable errors caused by defects in the source pattern. These repeatable errors create unusable disk regions in the same places on every disk produced. These regions would be highly prone to data errors if they were used for data recording. Therefore, it would be advantageous to “map out” these regions on the disks, just as is done on a disk-by-disk basis for conventional media in hard disk drives (HDDs) today.
For conventional media, the process of “mapping out” defects is done on a 100%, disk-by-disk basis, after the drives are constructed. By using heads to read and write data while scanning over the entire surfaces of the disks in the HDD, a manufacturing test system finds the defective areas on each surface of every disk and creates a table that is stored in the drive. During normal operation, the drive avoids the defective areas of the disk for all read/write requirements.
In the prior art, Japanese Publication No. JP11167751 discloses an optical disk system having a table of known defects that is stored on the removable optical media. The table is limited to describing the defects inherited directly from a device used to make the optical disk (i.e., the stamper). This reference also acknowledges the pre-emptive mapping out of sectors that are physically close to other known defects on the optical disk. Although this solution is workable for some applications such as removable optical disks, a comprehensive system for tracking and segregating inherent, multi-generational defects through large scale production of magnetic media would be desirable.